Continuous spray casting

Abstract

The present invention is an improvement over, and an adaptation to continuous casting, of known processes in which a molten metal such as steel is atomized under non-oxydizing conditions and projected at high velocity against a suitable target. The distance to the target is such that the atomized particles solidify on their way and hit the target in a solid, yet still plastic, state to be welded onto said target by their kinetic energy. Applicant has found a way to adapt such process to continuous operation, and more particularly, to production of wide slabs of great length and relatively small thickness, say, typical 1.5"×60" section and achieving that at great speeds of operation, such as 100 to 500 tons per hour which speed makes it possible to place it upstream of a continuous hot strip mill and thus produce, say, 0.060"×60" strips in one continuous operation, from molten metal. (Such mills cannot maintain their thermal balance if the speed of the workpiece is too slow). Another feature of the subject process is that it lends itself to an easy recuperation of the heat of fusion of the metal and of a substantial part of the heat contained in the product.

I claim: 
     
       1. A method of continuously producing a single metallic strip product of unlimited length from molten steel comprising the steps of providing a heat absorbing target having a cylindrical target surface with a vertical axis, locating means axially of said target surface for projecting a stream of molten particles against said target surface, providing a heat absorbing upper horizontal plane above said projecting means and a heat absorbing lower horizontal plane below said projecting means, said upper and lower planes cooperating with said target surface to form a chamber, maintaining a non-oxidizing atmosphere within said chamber, rapidly rotating and vertically oscillating said projecting means and said stream of molten particles produced thereby to deposit on said target surface a layer of metallic particles substantially only one particle deep to assure that all the particles of said layer reach a crystalizing stage before the deposition of another layer thereon, similarly depositing subsequent layers until the product of required thickness is produced, providing said target surface with a diameter such that at least half of said particles are solid and plastic when they hit said target surface, rotating said target and said product formed thereon, and withdrawing said metallic product as a single strip. 
     
     
       2. The method claimed in claim 1 including the step of providing said projecting means in the form of an atomizing head rotatable about said axis of said target surface, feeding molten metal to said head axially from above said head, providing said head with a spoon-shaped surface deep enough for effective acceleration of atomized particles of said molten metal by centrifugal force, providing said spoon-shaped surface with a plurality of sawtooth-section teeth extending transversely thereof and a hollow chamber therebeneath, providing a non-oxidizing gas, under pressure and in excess quantity over that needed for atomization of said molten metal, to said chamber to cool said spoon-shaped toothed surface and directing said gas from said chamber through at least two nozzles at one end of said spoon-shaped surface and along said teeth to increase turbulance of said gas from said nozzle and to assure atomization of said molten metal and deflection thereof to prevent contact of said molten metal with said teeth, and rotating said atomizer head such that said turbulent gas flow and centrifugal force direct said atomized metal substantially horizontally toward said target surface. 
     
     
       3. The method claim in claim 1 wherein said heat absorbing target comprises an annular member providing a vertical cylindrical target surface and including the steps of depositing said layers on said target in the form of a product tube, vertically oscillating said target so that said product tube continuously shifts downwardly from said target surface and below said lower plane, supporting the lower edge of said product tube while slowly rotating it and cutting said product tube along a helical line to produce said product strip. 
     
     
       4. The method claimed in claim 1 wherein said target comprises an endless belt conveyor, and including the steps of constantly rotating said belt conveyor about closely spaced entrance and exit pulleys, guiding a first flight of said belt conveyor between said entrance and exit pulleys in a cylindrical path of travel so as to form said vertical target surface, guiding the remainder of said belt conveyor in a second flight exteriorly of said first flight from said exit pulley to said entrance pulley, forming said strip product on said first flight between said upper and lower planes by said rotating and oscillating projecting means, and removing said product strip from said first flight of said belt conveyor near said exit pulley. 
     
     
       5. The method claimed in claim 3 including the step of providing said projecting means in the form of an atomizing head rotatable about said axis of said target surface, feeding molten metal to said head axially from above said head, providing said head with a spoon-shaped surface deep enough for effective acceleration of atomized particles of said molten metal by centrifugal force, providing said spoon-shaped surface with a plurality of sawtooth-section teeth extending transversely thereof and a hollow chamber therebeneath, providing a non-oxidizing gas, under pressure and in excess quantity over that needed for atomization of said molten metal, to said chamber to cool said spoon-shaped toothed surface and directing said gas from said chamber through at least two nozzles at one end of said spoon-shaped surface and along said teeth to increase turbulance of said gas from said nozzle and to assure atomization of said molten metal and deflection thereof to prevent contact of said molten metal with said teeth, and rotating said atomizer head such that said turbulent gas flow and centrifugal force direct said atomized metal substantially horizontally toward said target surface. 
     
     
       6. The method claim in claim 3 including the step of adjusting the pitch of said helical cutting line to determine the width of said product strip. 
     
     
       7. The method claimed in claim 3 including the step of providing concentric heat absorbing fences adjacent the inside and outside surfaces of said product tube below said lower plane to recuperate heat therefrom predominantly by radiation. 
     
     
       8. The method claimed in claim 4 including the step of providing said projecting means in the form of an atomizing head rotatable about said axis of said target surface, feeding molten metal to said head axially from above said head, providing said head with a spoon-shaped surface deep enough for effective acceleration of atomized particles of said molten metal by centrifugal force, providing said spoon-shaped surface with a plurality of sawtooth-section teeth extending transversely thereof and a hollow chamber therebeneath, providing a non-oxidizing gas, under pressure and in excess quantity over that needed for atomization of said molten metal, to said chamber to cool said spoon-shaped toothed surface and directing said gas from said chamber through at least two nozzles at one end of said spoon-shaped surface and along said teeth to increase turbulance of said gas from said nozzle and to assure atomization of said molten metal and deflection thereof to prevent contact of said molten metal with said teeth, and rotating said atomizer head such that said turbulent gas flow and centrifugal force direct said atomized metal substantially horizontally toward said target surface. 
     
     
       9. The method claimed in claim 4 including the steps of adjusting the vertical position of said upper horizontal plane and the oscillating of said projecting means to determine the width of said product strip.